Sustainable Multi-Hazard UK Sea Level Monitoring Network

The National Oceanography Centre (NOC) aims to establish a small Sustainable Multi-Hazard UK Sea Level Monitoring (SMUK SLM) network at 7 key locations with the aims of: (1) restoring continuity and accuracy of UK sea level observations across more than a century (2) answering key research questions associated with UK climate change-related sea level hazards and (3) addressing major information gaps in UK sea level science. Sea levels vary on multiple timescales, from high frequency waves, tides, storm surges and tsunami events, to seasonal and interannual changes and longer-term trends associated with climate change. In the UK, mean sea level changes are thought to the primary driver of increases in future extreme sea levels and coastal flooding [Horsburgh et al., 2020], because higher baseline sea levels will exacerbate the flood risk presented by other hazards, like storm surges. However, rates of UK sea level rise vary geographically, due to changes in local land levels associated with ice unloading from the last glaciation and processes like mining or subsidence. A sea level monitoring network of coastal tide gauges and co-located land level monitoring systems should capture the full extent of spatial and temporal variability in sea level and vertical land motion (VLM) that is needed to evaluate and mitigate these hazards. Historically, 7 of the longest UK records from the UK Tide Gauge Network (UKTGN) have contributed to periodic global, regional and local analyses of sea level change, including those of the Intergovernmental Panel on Climate Change (IPCC) and the annual State of the UK Climate reports produced by the NOC and the UK Met Office (UKMO) [Kendon et al., 2023]. However, UKTGN data quality has deteriorated in recent years and the network no longer meets the instrumentation and accuracy standards demanded for monitoring mm-scale trends in sea level for climate resilience. This is exacerbated by insufficient land motion observations at tide gauges which is one of the largest areas of uncertainty when estimating these trends. A further limitation is the inadequacy of the UKTGN sampling regime for capturing high frequency events like tsunamis or the full extent of tidal and storm surge extremes, presenting an information gap in the evaluation of sea level hazards and constraining our ability to evaluate and forecast how these might evolve in the context of global mean sea level rise. Consequently, in 2021 the NOC installed high accuracy, tsunami-capable tide gauges at 3 of the 7 key UK sites (Liverpool, Sheerness and Newlyn). These state-of-the-art gauges monitor sea level, VLM, atmospheric pressure and wave parameters, harnessing innovative techniques that minimise maintenance requirements. The above-water design presents no pollution risk, has a 30+year lifetime and utilises renewable (solar and wind-based) power solutions for sustainability. The high frequency, low latency observations support early identification of tsunamis and other sea level hazards delivering data to major public interest, international early warning and research data portals. In this project we aim to complete the SMUK SLM network, by installing comparable systems at the remaining 4 of the 7 sites (Aberdeen, Lerwick, North Shields and Stornoway). This will both restore and enhance scientific ability to estimate UK sea level rise and to better define and mitigate the risks pertaining to other UK sea level hazards, thus improving advice to decisionmakers and safeguarding coastal populations, environments, commerce and infrastructure.